In manufacturing semiconductor devices, lithography technique is used for a pattern formation. Conventionally, reduction projecting lithography technique wherein a mask is used is mainly used as the lithography technique. The reduction projecting lithography technique can achieve high throughput. However, the reduction projecting lithography technique needs an expensive mask set, which may be several decade million yen to one hundred million yen. In the present semiconductor industry, general LSI has been changed to system LSI, which is manufactured mainly through small-amount but many-kinds production. Thus, it is difficult to regain the high mask cost. In addition, mask manufacturing time is as long as one month, which is fatal in the system LSI that requires short TAT (turn-around time).
As a new-era lithography technique that solves the above problem, electron-beam direct writing technique has been paid attention to. According to the electron-beam direct writing technique, it is unnecessary to use an expensive mask, differently from the conventional reduction projecting lithography technique, but it is possible to form a minute pattern of 0.15 μm or smaller. That is, the above problem caused by the mask can be solved. However, the electron-beam direct writing technique has a defect of low throughput.
A character-projection (CP) type of technique has been proposed as a technique of improving the throughput in the electron-beam lithography technique. In that technique, a transfer mask for exposure, which is called a CP aperture mask and has a lot of various-character-patterned cells, is formed, and a semiconductor wafer is exposed to an electron beam selectively through a specific character pattern of the CP aperture mask. Thus, a pattern can be exposed at the one-time exposure step, although the pattern needs a lot of beam shots by the conventional variable shape writing manner or the like. Thus, the writing speed can be remarkably increased. That is, the throughput can be remarkably enhanced.
However, in the character-projection type of technique, various character patterns have to be formed in the CP aperture mask in advance. Thus, if a user wants to change a pattern to another, or if a part of the cells has a defect or the like, the whole CP aperture mask has to be manufactured from the beginning. This is a problem in view of cost and delivery time of the CP aperture mask.